1. Field of the Invention
The present invention relates to an axial-flow rotating machine provided with a transonic blade used in a flow field where an overall or partial flow has a transonic speed or higher.
2. Description of the Related Art
In the context of increased fuel cost and of the raising of environmental awareness in recent years, the importance of improved efficiency has been raised in axial-flow rotating machines such as industrial gas turbines and jet engines. One of means of improving efficiency in the axial-flow rotating machine is to reduce a blade loss. The blade loss is classified roughly into a profile loss occurring at a cross-sectional surface (airfoil) of a blade in the radial direction of a rotating shaft and the other losses. Examples of the other losses include a shock loss and a secondary loss. The recent axial-flow rotating machines have a large load per one stage and an increased Mach number of working fluid flowing into a blade. Therefore, the shock loss tends to increase. In other words, a reduction in shock loss largely contributes to an improvement in performance of the rotating machine.
The studies of reducing a shock loss have been made in the past. One of them is to modify a stacking line shape. JP-7-224794-A describes a blade whose stacking line is tilted toward the upstream side. JP-2008-115736-A describes a blade in which cross-sectional surfaces from a mean cross-sectional surface to a hub cross-sectional surface and a tip cross-sectional surface are shifted toward the upstream side to form an S-shaped stacking line and an amount of shifting the tip cross-sectional surface is maximized.